big bored 2cylinder 40hp

[iwanajohnson]

I need some help? :confused: I'm trying to find the biggest piston I can put in my 40hp 2 cylinder johnson. it's a 1994 model. It has 3.187" pistons in it now put I want to big bore it at least a .100 thousands over if I can. I just don't know if I can or not because the biggest I can find are .30 thousands over. I would really like to end up with some 3.387" pistons in it:D In the end I want want a little 2 clyinder that will make 3 clyinders cry:D (or at least the merc guys):p Thanks.

[DKL]

3.217 is about the largest you can go as far as I know with what pistons are available. There are other things you can do to get the power you are looking for. I wouldn't go more than .030, walls get to thin

[DKL]

You got the wrong block for power , sent you a PM

[iwanajohnson]

see my whole idea is to pull the sleeve out bore the water jaket out a bit and slip a blank sleeve in. Then bore it over and port it. Thats about the cheapest and easyest way I can see to get alot more power.

[DKL]

Good luck with that endever, just look for the block I told you about, you don't have to change the mid and pump, use the internals from the 40 if you must, they are the same, its the block and carbs thats different.

[iwanajohnson]

well i'm thinken about getting some port work done in the first place. and I was thinking about getting diffrent carbs?? I don't know I found a web site called www.madmanengineering.com that does port work and stuff like that they claim they can get a 20% or more boost in power by porting it? I'm probly going to check into that. I'll get something done to the motor before to long. aint in to big a hurry.

[Fast Fred]

try 2.4 merc pistons, mite just bore it out to fit, how thin is to thin on the sleeve, ? think .060-.080 thou should hold on for a wile. try to keep the stock rod, check skirt hight, wrist pin... think its close.

thing with modas like that, once thay blow up, ya need a bunch of new parts to start over:eek: :cool:

[iwanajohnson]

yea that is true. I took a look at that piston and it does look like it would work. Not for sure on the wrist pin diam. or that? do you think boring that much would help it much. See I want to have the benifits of a big 3 cylinder (big for my area 40hp motor resriction FUN FUN:mad: ) with the wieght of a 2cylinder short shaft:cool: . Is there any thing else that would help enough to be noticed but not cost an arm and a leg? Well for now I'm going to look into that merc piston. Thanks

[Fast Fred]

ya got to cut the skirt down, think the wrist pin was like +.010, was thinkin machine out the small end of the rod, then ya can use all the factory stuff ( the OMC bearin and the Merc pin on the stock rod) makes that part easy.

you got to get the Merc fire ring on thare to seal it up, that can be tricky;)

jet pump needs, wants, gots to have, Torque, low rpm. giant bullets would for sure make Big torque.

[iwanajohnson]

Hey fred thanks for that info:D . BUt do you think the rod will hold out doing that to it? Should I get some port work done? Would ceramic ball bearings help the crank any. Only experince Ive had with ceramic ball bearings is on my rc car. It screamed after I put them on it. But I don't know how much they would help my motor? Thanks agian for that info it helped me out alot.:D

[Fast Fred]

the rod would hold. the ports are guna have to be touched up , DO IT YOUR SELF, put the piston in a pipe with the skirt stickin out, run it through the ban-saw , 2.4 pistons are top guide, thats got to go, make a jig use a router and a wood bit(new) alu cuttin wax, and you can Hand machine them out, with the jigs, pipe jig, router jig, you can make them all the same and keep makin them. have the rod over sized on the small end to take the merc pin at a machine shop. mesure it all, to make reasonably sure it will work, i think it mite,
but i do not Know for sure.;)

[JohnsonM50]

well i'm thinken about getting some port work done in the first place. and I was thinking about getting diffrent carbs?? I don't know I found a web site called www.madmanengineering.com that does port work and stuff like that they claim they can get a 20% or more boost in power by porting it? I'm probly going to check into that. I'll get something done to the motor before to long. aint in to big a hurry.

Hey Iwana J, Are ya runnin your boat with whats on it? Hope so, enjoy what ya got while lookin for mores how I see it. Thanks for posting MME, very interesting. Im always lookin for more out of my 35 OMCs, have asked Qs about porting. Best I hear is to is to carefully mark and square w/o changing the timing. Otherwise.. hit or miss -favoring miss.
Ill be calling them too, I use these motors on a runnabout and a hydro.

[iwanajohnson]

Well i measured it and my sleeve will be way to thin. Now what? How I see it I can pull the sleeve, bore out the water jaket slip in a new sleeve and port it to my motor. Second I could pull the sleeve, have the water jacket chrome plated (if I could even have it done) [:confused:] I like to think outside the box. TO DANG CRAMPED IN THERE.:D What should I do about bearing for my crank. Got to looking and one is split in half. I was thinking ceramic maybe or sould I go stock OMC bearings? Oh yeah, not sure what "top guided pistons" are?

[iwanajohnson]

Can't enjoy running it when it's tore apart in the basment with scares in the cylinder so bad .030" won't clean it out. Fun Fun.

[JohnsonM50]

Can't enjoy running it when it's tore apart in the basment with scares in the cylinder so bad .030" won't clean it out. Fun Fun. Ouch!! maybe a second runner will turn up.

[Fast Fred]

a Nicacil lined alu cyl, chrome you got to change the rings, nic i'm thinkin runs the same rings as steel bore.that got twin two banger on it?:eek: :cool:

[iwanajohnson]

well what i was thinking was pull the sleeve out Chrome or nicelcadem the inside of the water jacket and not use a sleeve because the sleeve will be way to thin. If i was to do it like this I could put a bigger piston in it. I think a 140hp v4 omc would work? It is a 3.500" piston. the bigger the better.:D Don't know if it would work tell me what you think.:cool:

[Fast Fred]

thinkin 3.50 is guna be too big, a 3.377 up to +.030 2.4 liter piston be a better bet. :cool:

[iwanajohnson]

well I still want to know can I pull the sleeve out and nic. the liner and run it without sleeves or will the pressure be to much for it without the sleeve? Thanks:confused:

[iwanajohnson]

Looks like my little brother has been thinkin up some crazy stuff and runnin it through my name. hehe. He's been tellin me about this a lot but I've been so busy with work and huntin that I've been away from the computer for a few months. He's got the 2 cylinder he's playin with but I'm stickin to my guns at the 3 cylinder.